Window channels are commonly employed to mate glass to a window frame. These window channels are typically soft, resilient materials that provide structural integrity and often advantageously provide an environmental or acoustical seal. As a result, many window channels are referred to as weather seals.
In certain uses, such as in automobiles and the like, the weather seal also provides a surface against which a retractable window can slide and seal. In addition to providing an adequate seal, it is desirable that the weather seal is abrasion resistant and demonstrates a low coefficient friction.
In one instance, window channels are enhanced with a slip coat that may include a polymeric film or layer that is applied over a substrate layer, which is typically a rubbery material. For example, U.S. Pat. No. 5,447,671 teaches a weather seal that includes a contacting layer applied to a substrate. The substrate comprises a resilient and flexible synthetic resin or synthetic rubber, and the contacting layer may include a blend of high molecular weight polyethylene (300,000 g/mol) and ultra-high molecular weight polyethylene (1,300,000 g/mol). This patent suggests that the distinct polyethylene resins result in a rough contacting surface, which ostensibly is believed to reduce friction.
In order to overcome disadvantages that may be associated with the use of ultra-high molecular weight resins, such as ultra-high molecular weight polyethylenes, U.S. Pat. No. 6,146,739 teaches a glass-run channel that includes a contact part that includes a substrate layer and a slide-resin layer. The substrate layer includes a thermoplastic elastomer (e.g., a blend of a rubber and thermoplastic resin), and the slide-resin layer includes an ultra-high molecular weight polyolefin having an intrinsic viscosity of 7 to 40 dl/g as measured in a solvent at 135° C. decalin (which is assumed to include polymers having a weight average molecular weight in excess of about 400,000 g/mol, where the equivalency is based upon an empirical assessment of a range of polymers), a polyolefin having an intrinsic viscosity of 0.1 to 5 dl/g as measured in a solvent at 135° C. decalin, and a thermoplastic elastomer that includes a rubber and a thermoplastic resin.
Despite advancements that have been made thus far in the art, there remains a need to improve weather seals and particularly the slip coatings of the weather seals. In particular, there remains a need to improve the coefficient of friction of these slip coatings as well as the surface characteristics of these coatings such as their appearance.